61378: log,debug: fix `logspy`, new HTTP API to change `vmodule` r=stevendanna,tbg,andreimatei a=miretskiy

Fixes #61335.
First 3 commits from #66096.

**tldr: the logspy endpoint does not enable maximum verbosity any more, and now returns JSON entries. Use the new vmodule endpoint to configure verbosity if needed.**

See the commit messages of the last 2 commits for details and rationales.

Relevant user-facing changes:

**Release note (security update):** All the logging output to files
or network sinks was previously disabled temporarily while an operator
was using the `/debug/logspy` HTTP API, resulting in lost entries
and a breach of auditability guarantees. This behavior has been corrected.

**Release note (bug fix):** Log entries are not lost any more while the
`/debug/logspy` HTTP API is being used. This bug had existed since
CockroachDB v1.1.

**Release note (api change):** The `/debug/logspy` HTTP API has changed.
The endpoint now returns JSON data by default.
This change is motivated as follows:

- the previous format, `crdb-v1`, cannot be parsed reliably.
- using JSON entries guarantees that the text of each entry
  all fits on a single line of output (newline characters
  inside the messages are escaped). This makes filtering
  easier and more reliable.
- using JSON enables the user to apply `jq` on the output, for
  example via `curl -s .../debug/logspy | jq ...`

If the previous format is desired, the user can pass the query
argument `&flatten=1` to the `logspy` URL to obtain the previous flat
text format (`crdb-v1`) instead.

**Release note (api change)**: The `/debug/logspy` API does not any more
enable maximum logging verbosity automatically. To change the
verbosity, use the new `/debug/vmodule` endpoint or pass the
`&vmodule=` query parameter to the `/debug/logspy` endpoint.

For example, suppose you wish to run a 20s logspy session:

- Before:

  ```
  curl 'https://.../debug/logspy?duration=20s&...'
  ```

- Now:

  ```
  curl 'https://.../debug/logspy?duration=20s&vmodule=...'
  ```

  OR

  ```
  curl 'https://.../debug/vmodule?duration=22s&vmodule=...'
  curl 'https://.../debug/logspy?duration=20s'
  ```

As for the regular `vmodule` command-line flag, the maximum verbosity
across all the source code can be selected with the pattern `*=4`.

Note: at most one in-flight HTTP API request is allowed to modify the
`vmodule` parameter. This maintain the invariant that the
configuration restored at the end of each request is the same as when
the request started.

**Release note (api change)**: The new `/debug/vmodule` API makes it
possible for an operator to configure the logging verbosity in a
similar way as the SQL built-in function
`crdb_internal.set_vmodule()`, or to query the current configuration
as in `crdb_internal.get_vmodule()`. Additionally, any configuration
change performed via this API can be automatically reverted after a
configurable delay. The API forms are:

- `/debug/vmodule` - retrieve the current configuration.
- `/debug/vmodule?set=[vmodule config]&duration=[duration]` - change
  the configuration to `[vmodule config]` . The previous configuration
  at the time the `/debug/vmodule` request started is restored after
  `[duration]`. This duration, if not specified, defaults to twice the
  default duration of a `logspy` request (currently, the `logspy`
  default duration is 5s, so the `vmodule` default duration is 10s).
  If the duration is zero or negative, the previous configuration
  is never restored.

65648: sqlliveness/slstorage: break InternalExecutor depedency r=knz a=ajwerner

There was no fundamental reason to rely on SQL for this low-level subsystem.

Release note: None

66273: storageccl: don't update file registry when creating unencrypted files r=jbowens a=andyyang890

This patch changes PebbleFileRegistry to not store an entry
for an unencrypted file. This should lead to a performance
improvement since the file registry is rewritten every time
it is updated.

Fixes #65430.

Release note: None

Co-authored-by: Raphael 'kena' Poss <knz@thaumogen.net>
Co-authored-by: Andrew Werner <awerner32@gmail.com>
Co-authored-by: Andy Yang <ayang@cockroachlabs.com>